Flexible plastic bags are known in the art for carrying flexible articles such as disposable diapers, incontinent briefs, and catamenial pads. These flexible articles may be compressed while being inserted into the plastic bag so that transportation, storing, marketing, and consumption of the product are more convenient. However, opening plastic bags containing such compressed articles can be quite difficult. The greater the amount of compression, the stronger the bag must be, and hence the more difficult the bag is to open. Parents are familiar with the difficult experience of controlling a wiggling infant with one hand while attempting to open a bag of diapers with the other hand. Several diaper bags have been produced which include lines of perforations therein so that the bag can be easily opened. Incorporating perforations in such a bag, however, is disadvantageous where the articles within the bag are highly compressed, i.e., compressed in thickness 25%, or preferably 50% or more, relative to their initial uncompressed thickness. A plastic bag with perforations containing such highly compressed articles may burst open if dropped during transportation or if exposed to rough handling. Therefore, what is needed is a plastic bag which is easy to open yet strong enough to contain flexible articles, preferably compressed articles, and most preferably highly compressed articles.
In FIG. 1, a flexible plastic bag containing compressed disposable diapers exerts a force in the direction of arrow A since this is the compression direction of the diapers. Compressive forces are usually applied perpendicular to the planes into which articles are folded. The force A creates a circumferential force in the bag plastic around the outside of the bag. Therefore, perforations or areas of weakened plastic which are disposed perpendicular to the circumferential force tend to weaken the bag, and the bag will tend to burst open if the circumferential forces are greater than the resistive forces in the plastic. U.S. Pat. No. 4,934,535 describes a diaper bag which exposes this problem. This patent discloses a side-opening mechanism in which a portion of the side panel and a portion of the top gusset are torn away along oval-shaped perforation lines. These bags, however, may be subject to bursting because 75 percent of the side panel is surrounded by perforations substantially perpendicular to the direction of the circumferential forces and the side panel is therefore in a weakened state.
U.S. Pat. No. 5,036,978 also relates to an opening device for flexible plastic bags wherein a large portion of the side panel is surrounded by lines of perforations. Again, such bags may be subject to bursting during transportation.
German Patent G 89 15 566.1 relates to a tubular plastic bag in which a tear strip is formed at the top of the bag along three sides thereof. After the tear strip has been removed, the bag top may be rotated upward around the still-affixed side, much like a box lid. If used with compressed articles, however, this structure does nothing to release any of the compression forces, and consequently removing compressed articles from such a bag would be quite difficult.
International Patent Publication No. WO 91/08962 also relates to a flexible plastic bag with an opening feature in the side panel. FIGS. 1 and 2 indicate that a large portion of the side panel may be rotated upward about the bag top to allow the flexible articles to protrude through the resultant side opening. This is somewhat similar to the bag disclosed in U.S. Pat. No. 4,934,535 discussed above, and may be subject to bursting.
German Patent G 91 05 943.7 pertains to a flexible plastic bag having an opening feature extending from the front panel across the side panel to the rear panel. In FIG. 1, a tear-open tongue 7 extends around the end of the bag and is started with a flap handle 11. This bag disposes the lines of perforations parallel to the direction of the circumferential forces, but introduces an inherent weakness at the flap handle 11. Flap handle 11 may catch on other structure during handling allowing the bag to open prematurely. In addition, very little of the compression force is released upon opening of this bag, and removing compressed articles therefrom would be difficult.
German Patent G 91 09 154.3 relates to a flexible plastic bag having lines of perforations extending from the front panel, across the top gusset and to the rear panel. These lines of perforations, however, are close together and extend orthogonal to the direction of the circumferential forces. This could result in bursting of the bag. In addition, although FIG. 2 of this German Patent document relates to a flexible plastic bag including a loop handle, there are no perforations in the loop handle. This would make opening such a bag difficult, and would make removing products from such a bag very difficult.
Thus, what is needed is a flexible plastic bag which is easy to open, preferably capable of containing compressed or highly compressed articles, yet is easy to manufacture with high-speed automated machinery.